Hard disk assemblies for disk drives usually involve some form of clamping member to secure one or more disks to a hub, which in some instances may be part of a rotor of a motor or in other instances may be a disk hub adapted for attachment directly to a motor rotor or shaft.
The U.S. patents to Matsudaira et al U.S. Pat. Nos. 4,945,432, and Wood et al 5,031,062 are examples of disk attachments to a hub in which a plurality of disks are stacked and spaced on a cylindrical spindle hub which is part of the motor rotor. The disks are secured in compression between a bottom flange on the cylindrical spindle hub and a clamp at the top of the cylindrical spindle hub.
Examples of disk hub attachments to a motor shaft are found in the U.S. patent to Hasler et al U.S. Pat. Nos. 4,337,491, and to Angle et al 3,587,074.
The patent to Matsudaira et al, teaching the fabrication of a disk assembly employing a plurality of ceramic or glass disks, rather than metal disks, is concerned with the problem of compressional compliance in the disk stack between the lower flange on the cylindrical hub on which the disks are assembled and the top clamp. To this end, Matsudaira et al incorporates soft annular spacers between the individual disks and the metal spacer rings. The soft annular spacers include adhesives, O-rings and washers between the metal spacer rings and the disks in the stack.
The patentees Wood et al discuss the problems associated with disk stack fabrication in smaller form factor disk drives, mentioning particularly a 2.5 form factor. While structuring a disk stack in a manner somewhat similar to that of Matsudaira et al on a cylindrical spindle hub, between a bottom flange on that cylindrical spindle hub and a top clamp on that spindle hub, Wood et al addresses the problem of warping of the disk whenever clamping pressure is applied and employs a flowable material of some sort, including adhesives to fill in valleys in the surfaces on which the individual disks will seat. In this respect, Wood et al on their spacer ring 48, apply flowable material to both sides. When clamping pressure is applied to the disk stack assembled on the cylindrical spindle hub, the flowable material, filling in the valleys or depressions in those parts of the spindle hub and the spacer ring and the clamp engaging the disks, is described as minimizing disk warpage or ripple.
Older technology in hard disk assembly fabrication is represented in the patents to Angle et al and Hasler et al. The technology of Angle et al, dating back to the mid to late 1960s, describes the assembly of a single hard disk to a hub which is to be attached to the end of a motor shaft. The hub is provided with a flange against which the hard disk is seated. A wedge in the form of a split ring engages the opposite surface of the disk at the hub and fits into a circumferential V-shaped slot in the hub, in which position the hard wedge secures the disk against axial movement.
The patent to Hasler et al being, directed primarily to a description of a motor in connection with brushless DC fabrication of that motor, devotes little attention to the fabrication of a disk assembly, but provides within the cover of the disk drive assembly a pair of coaxially disposed axially spaced disks clamped in a hub which is adjustably and removably secured to the end of the motor shaft.
Structures such as these have limitations in their application to the smaller form factor disk drives, referring particularly to those scaled below the 2.5 form factor, referenced by the patentees Wood et al. There are limits, for example, to which the scale down of parts may be taken in fabricating the small form factor disk drives. Thus, structural simplification in disk assembly designs in small form factors is indicated.
An example of such simplification is found in a currently available 1.3 form factor disk drive in which adhesive bonding of one or more disks to a disk hub constitutes the sole means of attachment of the disks to the hub. This represents a very desirable solution to the fabrication of small form factor disk assemblies. It brings with it, however, in fabrication, the need for extreme care in the application of an adhesive to parts to be joined together to avoid drive contamination and, additionally, in the selection of an adhesive as the bonding agent, in which, ideally, there is rapid curing and zero out gassing in the long term.
The search for improvement and simplification in the design of fabrication of small form factor disk assemblies continues.